Wastewater treatment system and method

ABSTRACT

The invention is directed to a wastewater treatment system having an anoxic biological treatment zone, an aerobic biological treatment zone and a separator. The concentration of oxygen in streams within the system is strategically managed for improved removal of nutrient from the wastewater. A source of biodegradable carbon may be introduced to reduce the concentration of oxygen within the system. An effective treatment time under anoxic or aerobic conditions may further be varied.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and method for treatingwastewater, and more particularly to managing the concentration ofoxygen compounds in streams of a wastewater treatment system.

2. Discussion of Related Art

Wastewater treatment requirements continue to heighten in response tohealth and environment concerns regarding the impact of releasedeffluents. For example, effective conversion of phosphates andnitrogen-containing compounds, which may promote the growth of harmfulwater plants and algae, is often a primary objective of wastewatertreatment systems. Chemical precipitation techniques may be used forremoval of these pollutants but have associated high chemical costs.Biological treatment methods, employing microorganisms to convertpollutants, have emerged as an alternative approach.

For example, membrane bioreactors (MBRs) are gaining importance inwastewater treatment technology. MBRs may combine biological andphysical processes in one stage thus providing a compact, cost-effectiveand efficient solution capable of accommodating a wide range ofwastewater treatment applications. MBR systems typically involvebiological processes upstream of a membrane separator.

In general, biological wastewater treatment systems often consist ofanaerobic, anoxic and/or aerobic treatment zones in addition to aseparator. The presence of oxygen within biological wastewater treatmentsystems may benefit some biological processes while interfering withothers. Thus, strategic management of oxygen in streams within thewastewater treatment system may prove desirable.

BRIEF SUMMARY OF THE INVENTION

In accordance with one or more embodiments, the invention relates to asystem and method of treating wastewater.

In accordance with one or more embodiments, the invention relates to awastewater treatment system, comprising an anoxic treatment zone, anaerobic treatment zone fluidly connected to the anoxic treatment zone, aseparator fluidly connected to the aerobic treatment zone, and a meansfor varying an effective treatment time under anoxic conditions.

In accordance with one or more embodiments, the invention relates to awastewater treatment system, comprising a first biological treatmentzone, a second biological treatment zone fluidly connected to the firstbiological treatment zone, a membrane module comprising a filtermembrane fluidly connected to the second biological treatment zone, arecycle system fluidly connecting the membrane module to the firstbiological treatment zone, and a source of biodegradable carbon fluidlyconnected to the recycle system.

In accordance with one or more embodiments, the invention relates to awastewater treatment system, comprising a first biological treatmentzone, having an inlet and an outlet; a second biological treatment zone,having an inlet and an outlet, fluidly connected to the first biologicaltreatment zone; a third biological treatment zone, having an inlet andan outlet, fluidly connected to the second biological treatment zone;and a separator, having an inlet and an outlet, fluidly connected to thethird biological treatment zone. The outlet of the separator is fluidlyconnected to the inlet of the third biological treatment zone, and theoutlet of the third biological treatment zone is fluidly connected tothe inlet of the second biological treatment zone.

In accordance with one or more embodiments, the invention relates to amethod of treating wastewater, comprising anoxically treating thewastewater to produce a first water product, aerobically treating thefirst water product to produce a second water product, passing thesecond water product through a filter membrane to produce a concentratedmixed liquor and a filtrate, and reducing a concentration of dissolvedoxygen in at least a portion of the concentrated mixed liquor.

In accordance with one or more embodiments, the invention relates to amethod of treating wastewater, comprising introducing the wastewater toan anoxic treatment zone, introducing the wastewater exiting the anoxictreatment zone to an aerobic treatment zone, passing at least a portionof the wastewater exiting the aerobic treatment zone through a separatorto produce a concentrated mixed liquor and a filtrate, recycling atleast a portion of the concentrated mixed liquor to the aerobictreatment zone, and recycling at least a portion of the wastewater fromthe aerobic treatment zone to the anoxic treatment zone.

In accordance with one or more embodiments, the invention relates to amethod of treating wastewater, comprising contacting the wastewater withanoxic bacteria in an anoxic zone to produce a first water product,contacting the first water product with aerobic bacteria in an aerobiczone to produce a second water product, passing the second water productthrough a separator to produce a concentrated mixed liquor and afiltrate, establishing a first liquid circuit from an outlet of theseparator to an inlet of the aerobic zone, and establishing a secondliquid circuit from an outlet of the aerobic zone to an inlet of theanoxic zone.

In accordance with one or more embodiments, the invention relates to amethod of treating wastewater, comprising introducing the wastewater toan anoxic biological treatment zone, introducing the wastewater exitingthe anoxic biological treatment zone to an aerobic biological treatmentzone, passing at least a portion of the wastewater exiting the aerobicbiological treatment zone through a separator to produce a concentratedmixed liquor and a filtrate, and adjusting an effective volume of theanoxic biological treatment zone.

In accordance with one or more embodiments, the invention relates to awastewater treatment system, comprising an anoxic treatment zone, anaerobic treatment zone fluidly connected to the anoxic treatment zone, aseparator fluidly connected to the aerobic treatment zone, and acontroller in communication with an aeration system and configured togenerate a first aeration control signal to allow increase of aneffective volume of the anoxic treatment zone during a first biologicaltreatment mode of operation, and further configured to generate a secondaeration control signal to allow reduction of the effective volume ofthe anoxic treatment zone to a design condition during a secondbiological treatment mode of operation.

In accordance with one or more embodiments, the invention relates to amethod of facilitating treating wastewater, comprising providing awastewater treatment system, comprising a first biological treatmentzone, a second biological treatment zone fluidly connected to the firstbiological treatment zone, a membrane module comprising a filtermembrane fluidly connected to the second biological treatment zone, arecycle system fluidly connecting the membrane module to the firstbiological treatment zone, and a source of biodegradable carbon fluidlyconnected to the recycle system.

Other advantages, novel features and objects of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. Preferred, non-limiting embodiments of the present inventionwill be described with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram in accordance with one or more embodiments ofthe invention;

FIG. 2 is a block diagram in accordance with one or more embodiments ofthe invention illustrating a recycle regime for managing theconcentration of oxygen in streams within the system; and

FIG. 3 schematically illustrates a swing zone in accordance with one ormore embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components as set forth in thefollowing description or illustrated in the drawings. The invention iscapable of embodiments and of being practiced or carried out in variousways beyond those exemplarily presented herein.

In accordance with one or more embodiments, the invention relates to oneor more systems and methods for treating wastewater. In typicaloperation, the wastewater treatment system may receive wastewater from acommunity, industrial or residential source. For example, the wastewatermay be delivered from a municipal or other large-scale sewage system.Alternatively, the wastewater may be generated, for example, by foodprocessing or pulp and paper plants. The wastewater may be moved throughthe system by operation upstream or downstream of the system.

As used herein, the term “wastewater” refers to a stream of waste,bearing at least one undesirable constituent capable of being convertedby bacteria, deliverable to the wastewater treatment system fortreatment. More specifically, the undesirable constituent may be abiodegradable material, such as an inorganic or organic compound thatparticipates or is involved in the metabolism of a microorganism. Forexample, the undesirable constituent may include nitrate, nitrite,phosphorous, ammonia, and the like, typically present in wastewater. Thetype and concentration of undesirable constituents present in thewastewater may be site-specific. Communities may establish regulationsregarding these undesirable constituents. For the purposes of thepresent description, wastewater refers to what is fed to the system andwhat is treated throughout. Wastewater may be referred to herein, forexample, as a first, second or third water product.

As used herein, the term “wastewater treatment system” is a system,typically a biological treatment system, having a population ofmicroorganisms, including a diversity of types of bacteria, used todecompose biodegradable material. The conversion of pollutants toinnocuous compounds is typically facilitated or mediated by themicroorganisms as the wastewater is passed through the wastewatertreatment system. A biomass of microorganisms typically requires anenvironment that provides the proper conditions for growth or biologicalactivity.

According to one or more embodiments of the invention, the wastewatertreatment system of the present invention may be a bioreactor having oneor more treatment zones. As used herein, the term “treatment zone” isused to denote an individual treatment region, which can becharacterized as promoting, effecting, or exhibiting a type of metabolicactivity or biological process. Multiple treatment regions or zones maybe housed in a single vessel. Alternatively, a treatment region or zonemay be housed in a separate vessel, wherein a different treatment iscarried out in each separate vessel. The treatment zones may be sizedand shaped according to a desired application and to accommodate avolume of wastewater to be treated. For example, hydraulic residencetimes of various unit operations of the treatment system may depend onfactors such as influent flow rate, effluent requirements, concentrationof target compounds in the influent stream, temperature, and expectedpeak variations of any of these factors.

Each treatment zone may contain a fluidizable media to hostmicroorganisms. Each treatment zone may be maintained at differentconditions to enhance growth of different microorganisms. Without beingbound by any particular theory, different microorganisms may promotedifferent biological processes. For example, passing wastewater throughdenitrifying bacteria may increase the efficiency of a denitrifyingprocess. Likewise, passing wastewater through nitrifying bacteria mayincrease the efficiency of a nitrifying process. The bioreactor may alsocomprise means for maintaining the fluidizable media within eachtreatment zone during operation. For example, a screen, perforatedplate, baffle or fluid countercurrents may be used to maintain thefluidizable media within each treatment zone. The fluidizable media may,but need not be, similar in each treatment zone.

Prior to normal operation, the system may undergo a period of startup.Startup may involve biomass acclimation to establish a population ofbacteria. Startup may run from several minutes to several weeks, forexample, until a steady-state condition of biological activity has beenachieved in one or more treatment unit operations.

As mentioned, the bioreactor may comprise multiple biological treatmentzones. The bioreactor may comprise a first treatment zone. The firsttreatment zone may be an anaerobic treatment zone, maintained atanaerobic conditions to promote the growth and/or metabolic activity ofanaerobic bacteria. The term “anaerobic conditions” is used herein torefer, in general, to an absence of oxygen. The first treatment zone maybe maintained, for example, at less than 0.2 mg/L of dissolved oxygen(DO) content. The anaerobic bacteria may, for example, facilitate and/orenhance the efficiency of a phosphorous release bioprocess in which thebacteria may take up volatile fatty acids through a mechanism involvinghydrolysis and release of phosphate.

The bioreactor may also comprise a second treatment zone. The secondtreatment zone may be an anoxic treatment zone, maintained at anoxicconditions to promote the growth and/or metabolic activity of anoxicbacteria. The term “anoxic conditions” is used herein to refer, ingeneral, to a lack of oxygen. The second treatment zone may bemaintained, for example, at less than 0.5 mg/L DO content. The anoxicbacteria may, for example, facilitate and/or enhance the efficiency of adenitrification process in which the bacteria may reduce nitrate togaseous nitrogen while respiring organic matter.

The bioreactor may further comprise a third treatment zone. The thirdtreatment zone may be an aerobic treatment zone, maintained at aerobicconditions to promote the growth and/or metabolic activity of aerobicbacteria. The term “aerobic conditions” is used herein to refer, ingeneral, to the presence of oxygen. The aerobic bacteria may, forexample, facilitate and/or enhance the efficiency of a nitrifingbioprocess in which ammonia is oxidized to form nitrite which is in turnconverted to nitrate. The aerobic bacteria may also, for example,facilitate and/or enhance the efficiency of a phosphorous uptakebioprocess in which soluble phosphorous is restored to the bacteria.

The bioreactor may comprise additional treatment zones not hereinmentioned. Indeed, a plurality of the above-mentioned biologicaltreatment zones may be utilized in the treatment systems of theinvention. One or more treatment zones may be run simultaneously. One ormore treatment zones may be operated continuously or as a batch process.

The wastewater treatment system may also contain one or more separators.The separator may comprise one or more unit operations capable ofseparating a wastewater stream into one or more components. For example,the separator may filter and/or clarify a wastewater stream to produce aconcentrated mixed liquor and a filtrate. The separator may bepositioned downstream of one or more of the biological treatment zonesto act upon a wastewater stream after it has undergone biologicalprocesses and/or while it is undergoing biological processes. Forexample, the separator may be positioned downstream of an aerobictreatment zone. The separator may be housed in the same vessel as one ormore of the biological treatment zones. Alternatively, the separator maybe housed in a separate vessel apart from the bioreactor.

According to one or more embodiments, the wastewaster treatment systemmay be a membrane bioreactor system in which the separator may comprisea membrane operating system (MOS). The MOS may comprise one or moreporous or semi-permeable membrane. The membrane may be positioned so asto be submerged during operation and may have any configuration suitablefor a particular purpose, such as a sheet or hollow tube. The membranemay be formed of any material (natural or synthetic) suitable for aparticular filtration process. In one embodiment, for example, themembrane is formed of polymeric hollow fibers, such as those made ofpolyvinylidene fluoride polymer.

One or more membranes may be positioned in one or more membrane moduleswithin the MOS. The membrane modules may have any shape andcross-sectional area suitable for use in a desired application, forexample, square, rectangular or cylindrical. For example, membranemodules may be used such as those described in U.S. Pat. No. 6,872,305,which is incorporated herein by reference in its entirety. Multiplemembrane modules may be positioned adjacent to one another or atpredetermined positions within the MOS. The membrane modules may bepositioned at any angle, including vertical and horizontal, within theMOS. In one embodiment, a plurality of membrane modules may be mountedto a module support rack to facilitate membrane maintenance and/orreplacement.

In accordance with one or more embodiments of the wastewater treatmentsystem, an aerobic treatment zone may be fluidly connected downstream ofan anoxic treatment zone. A separator may be fluidly connecteddownstream of the aerobic treatment zone. An anaerobic treatment zonemay be fluidly connected upstream of the anoxic treatment zone. Thus,according to one or more embodiments, wastewater entering the wastewatertreatment system may pass through an anaerobic treatment zone, an anoxictreatment zone, an aerobic treatment zone and a separator, in series. Arecycle system may fluidly connect the separator, most typically aconcentrated mixed liquor exiting the separator, to any of theanaerobic, anoxic and/or aerobic treatment zones and may alsointerconnect the treatment zones.

In accordance with one or more embodiments of the present invention, thewastewater treatment system may strategically manage the concentrationof oxygen in streams within the system to facilitate pollutant removal.Oxygen may be present in various forms within the bioreactor. Forexample, streams within the system may contain dissolved oxygen and/oroxygenated species, such as, but not limited to, nitrates and nitrites,any of which may either originate in the wastewater or be produced bybiological processes occurring within the bioreactor. Without beingbound by any particular theory, the presence of oxygen may promotecertain biological processes, such as aerobic biological processes,while inhibiting others such as anaerobic biological processes. Morespecifically, oxygen may interfere with portions of metabolic schemesinvolved in the biological removal of nitrogen. Oxygen may alsointerfere with release of phosphorous, which may in turn limit theuptake of phosphorous. Thus, delivering wastewater streams with a highconcentration of oxygen to treatment zones where oxygen may promotebiological activity, and reducing the concentration of oxygen inwastewater streams delivered to treatment zones where oxygen caninterfere with biological processes, may be beneficial. Strategicmanagement of the concentration of oxygen in streams within thewastewater treatment system may allow reduced equipment size, fasterreaction rates and overall improved biological removal of pollutants.

Thus, in certain embodiments of the present invention, wastewaterstreams may be recycled within the system for additional treatment whilestrategically managing their oxygen concentration. For example, awastewater stream exiting a separator may be recycled to an aerobictreatment zone for further processing and to benefit from its oxygencontent because the presence of oxygen may be advantageous to biologicalprocesses occurring therein. Furthermore, a stream exiting an aerobictreatment zone, with a depleted oxygen concentration, may be recycled toanaerobic and/or anoxic treatment zones for further processing whereoxygen may interfere with biological processes occurring therein. Inthis way, the concentration of oxygen in streams within the treatmentsystem may be strategically managed to enhance removal of pollutantsfrom the wastewater.

Liquid circuits may operate within some embodiments of the presentinvention. As used herein, the term liquid circuit is intended to definea particular connection and arrangement of valves and lines that allowsa liquid stream to flow therein. A first liquid circuit may fluidlyconnect an outlet of the separator to an inlet of the aerobic treatmentzone. The first liquid circuit may therefore deliver a stream rich inoxygen to a treatment zone where oxygen may be beneficial to biologicalprocesses occurring therein. A second liquid circuit may fluidly connectan outlet of the aerobic treatment zone to an inlet of the anaerobicand/or anoxic treatment zones. Thus, the second liquid circuit maydeliver a wastewater stream with a depleted concentration of oxygen totreatment zones where oxygen may interfere with biological processesoccurring therein.

Certain embodiments of the present invention may also comprise a sourceof biodegradable carbon to aid in controlling the concentration ofoxygen within the wastewater treatment system. The biodegradable carbonmay be any metabolizable carbon capable of participating in orfacilitating biological activity of microorganisms. For example, thebiodegradable carbon can serve as an electron donor in metabolic schemesthat reduce the oxygen concentration of a liquor containing suchmicroorganisms. The carbon source may be, for example, methanol, sugar,raw sewage, acetone or any commercially available material for thispurpose, such as a MicroC™ methyl alcohol solution available fromEnvironmental Operating Solutions, Inc., Falmouth, Mass. Without beingbound by any particular theory, microorganisms in the wastewatertreatment system may consume the biodegradable carbon while depletingthe concentration of oxygen. Again, the oxygen may be found in variousforms within wastewater streams of the system, for example, as dissolvedoxygen or in oxygenated compounds not yet reduced by biologicalprocesses, such as nitrates. In some embodiments, the source ofbiodegradable carbon may be fluidly connected to one or more biologicaltreatment zones to reduce the concentration of oxygen entering thetreatment zone. For example, the source of biodegradable carbon may befluidly connected to an anoxic treatment zone and/or an anaerobictreatment zone.

According to some embodiments of the present invention, a feed ofbiodegradable carbon may be introduced to a wastewater stream enteringan anoxic treatment zone. There may be a retention period during whichthe wastewater stream remains in contact with the biodegradable carbonprior to blending with the wastewater in the remainder of the anoxictreatment zone in order to promote oxygen depletion. For example, abaffle or other means to increase residence time may be positionedwithin the anoxic treatment zone to provide this retention period.Further embodiments may involve one or more vessels that provide thedesired period. Depletion of oxygen may allow the anoxic treatment zoneto operate at a lower oxidation-reduction potential (ORP) condition,thus enabling the release of more soluble phosphorous for aerobicuptake. Depletion of oxygen may also increase the rate of reaction fordenitrification of nitrate in the anoxic treatment zone to attainoverall lower effluent concentrations of nitrate and total nitrogen.

The biodegradable carbon may be added in any manner. For example, thebiodegradable carbon may be metered directly into a wastewater streamwithin the system. Alternatively, the biodegradable carbon may be addedto the wastewater stream in a deoxygenation tank. The amount ofbiodegradable carbon fed to the wastewater treatment system may varybased on the wastewater treatment application. For example, the amountof biodegradable carbon added may be a quantity necessary to ensure thedepletion to a desired quantity of oxygen present in a wastewater streamwithin the system, such as 2 ppm of carbon per 1 ppm of oxygen. Certainembodiments of the present invention may include a sensor, for example aDO galvanic probe, a DO optical probe, an ORP probe, or other sensorwhich measures process conditions, to aid in detecting the concentrationof oxygen present at any point within the treatment system. The sensormay be positioned, for example, so as to determine the concentration ofoxygen in a wastewater stream entering an anoxic treatment zone.

Referring now to the drawings and, more particularly to FIG. 1 thereof,wastewater treatment system 100 is described which is constructed inaccordance with one or more embodiments of the present invention.Components of wastewater treatment system 100 may be made of anymaterial chemically and physically suitable for use in accordance withthe conditions of the invention.

Wastewater may enter the wastewater treatment system 100 from a source102 at any flow rate Q and system 100 may be sized to accommodate anyflow rate Q. Without being limited, it is believed that the flow rate Qmay be as high as 3 million gallons per day, and is more typicallybetween about 0.1 and 1.5 million gallons per day. The wastewater may beintroduced into a first treatment zone 110, which may be an anaerobictreatment zone, to form a first water product. At least a portion of thefirst water product may then be withdrawn from the first treatment zone110 and introduced as stream 112 into a second treatment zone 120, whichmay be an anoxic treatment zone, to form a second water product. A flowrate of stream 112 may be any multiple of Q. For example, in oneembodiment, the flow rate of stream 112 may be 3Q.

At least a portion of the second water product may then be withdrawnfrom the second treatment zone 120 and introduced as stream 122 into athird treatment zone 130, which may be an aerobic treatment zone, toform a third water product. A flow rate of stream 122 may be anymultiple of Q. For example, in one embodiment, the flow rate of stream122 may be 7Q. At least a portion of the third water product may then bewithdrawn from the third treatment zone 130 and introduced as stream 132into a separator 140. A flow rate of stream 132 may also be any multipleof Q. For example, in one embodiment, the flow rate of stream 132 may be7Q. One or more unit operations in separator 140 may separate stream 142into one or more components. For example, a filtrate and a concentratedmixed liquor may be produced by separator 140.

At least a portion of the concentrated mixed liquor exiting separator140 may be recycled to the first and/or second treatment zones 110, 120for additional treatment. The flow rate of the recycle stream may be anymultiple of influent flow rate Q. The volume of concentrated mixedliquor that is recycled may, for example, be determined based ondischarge requirements, influent flow rate, influent pollutantconcentration and/or a condition in the first and third treatment zones110, 130 and to some extent conditions in the second treatment zone 120.For example, in one embodiment, the concentrated mixed liquor fromseparator 140 may be recycled at a flow rate of 6Q. A source ofbiodegradable carbon, such as methanol, may be introduced to the streamof concentrated mixed liquor recycled from separator 140 to the firstand/or second treatment zones 110, 120 at streams 142, 144. The carbonfeed may aid in reducing the concentration of oxygen entering thesetreatment zones where oxygen may interfere with biological activity.

The flow rate of any stream entering or exiting any treatment zone mayvary based on operating conditions within the system 100. For example,the flow rate of stream 112 may vary based on factors such as influentflow rate Q and the volume of any recycle stream. Likewise, the flowrates of streams 122 and 132 may also vary. In general, the system 100may operate such that the total volume entering any one treatment zoneis equal to the total volume exiting that treatment zone.

FIG. 2 illustrates another embodiment of the present invention.Wastewater entering the wastewater treatment system 200 from source 202may be introduced into a first treatment zone 210, which may be ananaerobic biological treatment zone. The wastewater may then be treatedin a second treatment zone 220, which may be an anoxic biologicaltreatment zone, and be further treated in a third treatment zone 230,which may be an aerobic biological treatment zone. The wastewater maythen enter a separator 240 where it may undergo one or more unitoperations to be separated into one or more components. For example, theseparator may produce a filtrate and a concentrated mixed liquor.Nitrogen may be vented from the second treatment zone 220 at stream 250and waste activated sludge may be purged from the third treatment zone230 at stream 260.

Again, a portion of the concentrated mixed liquor exiting separator 240may be recycled for additional treatment, such as to meet dischargerequirements. Rather than delivering the concentrated mixed liquordirectly back to the first and/or second treatment zones 210, 220 forfurther processing, the concentrated mixed liquor may be strategicallyrecycled in a regime designed to enhance removal of pollutants from thewastewater through management of the oxygen concentration in streamswithin the system 200. A portion of the concentrated mixed liquor may berecycled as stream 242 to the third treatment zone 230 for additionaltreatment where its oxygen content may be beneficial to biologicalprocesses occurring therein. For an influent flow rate of Q, a flow rateof stream 242 may be any multiple of Q. The flow rate of stream 242 may,for example, be determined based on discharge requirements, influentflow rate, influent pollutant concentration, and/or conditions in any ofthe treatment zones. In one embodiment, for example, the flow rate ofstream 242 may be 6Q.

A portion of the wastewater exiting the third treatment zone 230, with adepleted oxygen concentration, may be recycled as stream 244 to thefirst and/or second treatment zones 210, 220 for additional treatmentwhere oxygen may interfere with biological processes occurring therein.Again, assuming an influent flow rate of Q, a flow rate of stream 244may be any multiple of Q. The flow rate of stream 244 may also, forexample, be determined based on discharge requirements, influent flowrate, influent pollutant concentration, and/or conditions in anytreatment zone. In one embodiment, for example, the flow rate of stream244 may be 4Q. Additionally, a source of biodegradable carbon, such asmethanol, may be introduced to the stream of wastewater recycled fromthe third treatment zone 230 to the first and/or second treatment zones210, 220 at 270 which may aid in further reducing the concentration ofoxygen entering these treatment zones.

Thus, a first liquid circuit may be established from an outlet of theseparator 240 to an inlet of the third treatment zone 230. A secondliquid circuit may be established from an outlet of the third treatmentzone 230 to an inlet of the first and/or second treatment zones 210,220. A controller (not shown) may be configured to generate controlsignals to establish the first and/or second liquid circuits. Forexample, the controller may be configured to generate a first controlsignal that establishes the first liquid circuit from an outlet ofseparator 240 to an inlet of the third treatment zone 230, and furtherconfigured to generate a second control signal that establishes thesecond liquid circuit from an outlet of the third treatment zone 230 toan inlet of the first and/or second treatment zone 210, 220.

Again, the flow rate of any stream entering or exiting any treatmentzone may vary based on operating conditions within the system 200. Ingeneral, the system 200 may operate such that the total volume enteringany one treatment zone is equal to the total volume exiting thattreatment zone.

Other embodiments of the present invention may include techniques thatfacilitate varying an effective treatment time under anoxic or aerobictreatment conditions within the system. As used herein, the term“effective treatment time” is used to describe a period of time duringwhich the wastewater is exposed to particular conditions. Variations ineffective treatment time under anoxic or aerobic treatment conditionsmay be desirable based upon variations in influent flow rate and/or theconcentration or level of one ore more relevant target compounds. Forexample, when the flow rate of wastewater entering the wastewatertreatment system decreases, nitrification may be less of a concern andso it may be desirable to focus on denitrification as facilitated byanoxic biological processes. This may enable the wastewater treatmentsystem to eliminate peaks of nitrogen that may result during periods ofhigher flow rate. Conversely, when flow rate of wastewater increases, itmay be more desirable to nitrify as facilitated by aerobic biologicalprocesses which may, in turn, feed denitrification biological processes.Thus, certain embodiments of the invention are directed to addressingseasonal and/or diurnal characteristics of the influent wastewaterstream. Certain embodiments of the present invention may include aflowmeter to aid in monitoring influent flow rate.

It may also be desirable to vary an effective treatment time underanoxic or aerobic treatment conditions based on fluctuations in aconcentration of a target constituent within the treatment system. Forexample, a high concentration of nitrate in the influent wastewaterstream may make it desirable to increase anoxic treatment time so thatthe system may be primarily efficient in eliminating nitrogen viadenitrification. Alternatively, if there is a high concentration ofammonia in the influent wastewater stream, it may be more desirable toincrease aerobic treatment time so that the system may be primarilyefficient in nitrifying the ammonia for further processing within thesystem. Certain embodiments of the present invention may include sensorsto aid in monitoring the concentration of target constituents in theinfluent wastewater stream. For example, the wastewater treatment systemmay include a COD, TOC, BOD and/or ammonia sensor.

The treatment system may extend and/or shorten the effective treatmenttime under anoxic or aerobic conditions from a design condition. As usedherein, the term “design condition” is used to refer to normal operatingconditions. Varying the effective treatment time under anoxic or aerobicconditions may be achieved using any technique capable of altering theduration of time during which the wastewater is exposed to anoxic oraerobic conditions. For example, varying the effective treatment timemay be facilitated by varying an effective residence time of awastewater stream under anoxic or aerobic conditions. This may beachieved, for example, by regulating the flow rate of one or morewastewater streams through one or more anoxic or aeration treatmentzones.

Alternatively, the system of the present invention may comprise anaeration system, in fluid communication with a biological treatmentzone, whereby a flow of air, or other oxygen-supplying stream, may beswitched on or off in at least a portion of the biological treatmentzone. The system may further prevent introduction of air, for examplefrom another biological treatment zone or source, after the flow of airhas been switched off. For example, one or more screens, perforatedplates, baffles and/or fluid countercurrents may be used within thebiological treatment zone to prevent the introduction of air.

The system may facilitate varying an effective treatment time underanoxic conditions by varying an effective volume of an anoxic treatmentzone. As used herein, the term “effective volume” is used to refer tothe volume of treatment zone maintained at anoxic or aerobic conditionsinto which the wastewater may be introduced. For example, the system maycomprise a controller in communication with an aeration system andconfigured to generate a first control signal to allow increase of aneffective volume of an anoxic treatment zone during a first biologicaltreatment mode of operation, and further configured to generate a secondaeration control signal to allow reduction of the effective volume ofthe anoxic treatment zone to, for example, a design condition during asecond biological treatment mode of operation.

FIG. 3 illustrates another embodiment of the present invention whereintreatment system 300 may comprise one or more swing zones 350 tofacilitate varying an effective treatment time, or volume, under anoxicor aerobic conditions. Swing zone 350 may be a biological treatment zonewherein a source of air (not shown) may be regulated. Without beingbound by any particular theory, introducing air within swing zone 350may result in aerobic treatment conditions within swing zone 350 whilereducing air may result in anoxic treatment conditions within swing zone350. Swing zone 350 may be positioned anywhere within treatment system300. For example, swing zone 350 may be positioned between an anoxictreatment zone 320 and an aerobic treatment zone 330 as illustrated.

The effective treatment time under anoxic or aerobic conditions may bevaried simultaneously with operation of the recycle regime and/or theintroduction of biodegradable carbon both discussed above.

It should be appreciated that numerous alterations, modifications andimprovements may be made to the illustrated systems and methods.

In all modes of operation, any compound may be added to the treatmentzones to promote and enhance the growth of bacteria capable of targetingpollutants in the wastewater stream to be treated.

The wastewater treatment system of the various embodiments of thepresent invention may also comprise anything capable of providing avolume to induce oxygen depletion within recycled wastewater streamsprior to re-introduction to the biological process, such as a vessel orpipe. For example, an oxygen depletion unit may be sized to accept aportion of the concentrated mixed liquor exiting the separator and/or aportion of a wastewater stream exiting the aerobic treatment zone. Theoxygen depletion unit may aid in controlling the oxygen content inwastewater streams delivered to treatment zones within the wastewatertreatment system where the presence of oxygen may interfere withbiological processes therein.

According to another embodiment, the wastewater treatment system maycomprise one or more pretreatment units. The one or more pretreatmentunits may be positioned typically upstream of the first treatment zone.The system may, for example, include one or more pretreatment unitsserving to screen an influent stream to collect solids or otherundesirable constituents, such as fats, oil and grease. In someembodiments, for example, the one or more pretreatment units may includea perforated plate continuous screen having 2 mm openings. Otherpretreatment units may involve chemical treatment systems which, forexample, precipitate, convert, or adjust a condition of an influentstream.

Some embodiments of the present invention may include one or moretreatment systems positioned upstream of the separator to facilitatefiltration and/or clarification. Other embodiments of the presentinvention may include one or more treatment systems positioneddownstream of the separator to further treat effluent before it isreleased from the system, such as a chemical treatment system. One ormore screening units may be used to prevent solids or other undesirableconstituents from entering the chemical treatment system.

According to another embodiment, the wastewater treatment system maycomprise a reserve storage tank fluidly connected to the bioreactor tonormalize flow into the bioreactor. The reserve storage tank may besized to accommodate fluctuations in wastewater generation.

Although various embodiments exemplarily shown have been described asusing sensors, it should be appreciated that the invention is not solimited. For example, rather than requiring any electronic orelectromechanical sensors, the measurement of various levels couldalternatively be based upon the senses of an operator.

In some embodiments, the wastewater treatment system can include sensorsfor measuring at least one property or operating condition of thesystem, such as sensors for measuring pH, temperature, salinity,turbidity, and pressure drop, for example, at different points in thesystem thus enabling further monitoring for system optimization.

In accordance with other embodiments of the present invention, thewastewater treatment system can also include one ore more controllersfor adjusting or regulating at least one operating parameter of thesystem or a component of the system, such as, but not limited to,actuating valves and pumps. The controller may be capable of monitoringand regulating the operating conditions of the wastewater treatmentsystem including its components. The controller may be in communicationwith one or more sensors. The controller is typically amicroprocessor-based device, such as a programmable logic controller(PLC) or a distributed control system, that receives and/or sends inputand output signals to and from components of the wastewater treatmentsystem. For example, the controller may control the introduction ofbiodegradable carbon. The controller may regulate the flow rate ofstreams within the wastewater treatment system. The controller maycontrol the amount of wastewater recycled throughout the wastewatertreatment system. The controller may also vary an effective volume of ananoxic or aerobic treatment zone within the wastewater treatment system.The controller may likewise vary an effective treatment time underanoxic or aerobic conditions within the wastewater treatment system.

The invention contemplates the modification of existing facilities toretrofit one or more systems, or components in order to implement thetechniques of the invention. Thus, for example, an existing facility canbe modified to include a controller executing instructions in accordancewith one or more embodiments exemplarily discussed herein.Alternatively, existing control systems can be reprogrammed or otherwisemodified to perform any one or more acts of the invention. Existingwastewater treatment systems can be converted to wastewater treatmentsystems in accordance with systems and techniques described hereinutilizing at least some preexisting equipment such as the shell andwetted parts. It is envisioned that the biodegradable carbon feedapproach could be retrofitted to existing facilities that were designedwithout any such provision without requiring significant constructionefforts. Likewise, a recycle system in accordance with embodiments ofthe present invention may be adapted to existing biological treatmentzones. A swing zone in accordance with one or more embodiments of thepresent invention could also be implemented in existing biologicaltreatment systems.

As used herein, the term “plurality” refers to two or more items orcomponents. The terms “comprising,” “including,” “carrying,” “having,”“containing,” and “involving,” whether in the written description or theclaims and the like, are open-ended terms, i.e., to mean “including butnot limited to.” Thus, the use of such terms is meant to encompass theitems listed thereafter, and equivalents thereof, as well as additionalitems. Only the transitional phrases “consisting of” and “consistingessentially of,” are closed or semi-closed transitional phrases,respectively, with respect to the claims.

Use of ordinal terms such as “first,” “second,” “third,” and the like inthe claims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Those skilled in the art should appreciate that the parameters andconfigurations described herein are exemplary and that actual parametersand/or configurations will depend on the specific application in whichthe systems and techniques of the invention are used. For example,wastewater treatment systems of the invention may further involve acombination of separation operations such as settlers and, in somecases, hydrocyclones. Those skilled in the art should also recognize, orbe able to ascertain, using no more than routine experimentation,equivalents to the specific embodiments of the invention. It istherefore to be understood that the embodiments described herein arepresented by way of example only and that, within the scope of theappended claims and equivalents thereto, the invention may be practicedotherwise than as specifically described.

1. A wastewater treatment system, comprising: an anoxic treatment zone;an aerobic treatment zone fluidly connected to the anoxic treatmentzone; a separator fluidly connected to the aerobic treatment zone; andmeans for varying an effective treatment time under anoxic conditions.2. The system of claim 1, wherein the separator comprises a membranemodule.
 3. The system of claim 1, further comprising a recycle systemfluidly connecting the separator to the anoxic treatment zone.
 4. Thesystem of claim 3, further comprising a source of biodegradable carbonfluidly connected to the recycle system. 5-16. (canceled)
 17. Awastewater treatment system, comprising: a first biological treatmentzone, having an inlet and an outlet; a second biological treatment zone,having an inlet and an outlet, fluidly connected to the first biologicaltreatment zone; a third biological treatment zone, having an inlet andan outlet, fluidly connected to the second biological treatment zone;and a separator, having an inlet and an outlet, fluidly connected to thethird biological treatment zone, wherein the outlet of the separator isfluidly connected to the inlet of the third biological treatment zone,and wherein the outlet of the third biological treatment zone is fluidlyconnected to the inlet of the second biological treatment zone.
 18. Thesystem of claim 17, wherein the outlet of the third biological treatmentzone is fluidly connected to the inlet of the first biological treatmentzone.
 19. The system of claim 17, further comprising a source ofbiodegradable carbon fluidly connected to the first and secondbiological treatment zones.
 20. The system of claim 19, wherein thebiodegradable carbon comprises methanol.
 21. A method of treatingwastewater, comprising: anoxically treating the wastewater to produce afirst water product; aerobically treating the first water product toproduce a second water product; passing the second water product througha filter membrane to produce a concentrated mixed liquor and a filtrate;and reducing a concentration of dissolved oxygen in at least a portionof the concentrated mixed liquor.
 22. The method of claim 21, furthercomprising anaerobically treating the wastewater prior to anoxicallytreating the wastewater.
 23. The method of claim 21, wherein the act ofreducing the concentration of dissolved oxygen comprises introducingbiodegradable carbon.
 24. The method of claim 23, wherein the act ofintroducing biodegradable carbon is performed based on an ORP signalfrom an ORP sensor.
 25. A method of treating wastewater, comprising:introducing the wastewater to an anoxic treatment zone; introducing thewastewater exiting the anoxic treatment zone to an aerobic treatmentzone; passing at least a portion of the wastewater exiting the aerobictreatment zone through a separator to produce a concentrated mixedliquor and a filtrate; recycling at least a portion of the concentratedmixed liquor to the aerobic treatment zone; and recycling at least aportion of the wastewater from the aerobic treatment zone to the anoxictreatment zone.
 26. The method of claim 25, further comprising reducinga concentration of dissolved oxygen in the wastewater recycled from theaerobic treatment zone to the anoxic treatment zone.
 27. The method ofclaim 26, wherein biodegradable carbon is introduced to the wastewaterrecycled from the aerobic treatment zone to the anoxic treatment zone.28. The method of claim 27, further comprising controlling an amount ofbiodegradable carbon introduced to the wastewater recycled from theaerobic treatment zone to the anoxic treatment zone based on an ORPsignal from an ORP sensor.
 29. The method of claim 27, furthercomprising controlling an amount of biodegradable carbon introduced tothe wastewater recycled from the aerobic treatment zone to the anoxictreatment zone based on a COD level of the wastewater.
 30. A method oftreating wastewater, comprising: contacting the wastewater with anoxicbacteria in an anoxic zone to produce a first water product; contactingthe first water product with aerobic bacteria in an aerobic zone toproduce a second water product; passing the second water product througha separator to produce a concentrated mixed liquor and a filtrate;establishing a first liquid circuit from an outlet of the separator toan inlet of the aerobic zone; and establishing a second liquid circuitfrom an outlet of the aerobic zone to an inlet of the anoxic zone. 31.The method of claim 30, further comprising introducing a source ofbiodegradable carbon to a liquid in the second liquid circuit.
 32. Themethod of claim 30, further comprising contacting the wastewater withanaerobic bacteria.
 33. The method of claim 30, wherein the act ofcontacting the wastewater with anoxic bacteria is performed during ananoxic treatment time period.
 34. The method of claim 31, wherein thesource of biodegradable carbon comprises methanol.
 35. The method ofclaim 31, wherein introducing the source of biodegradable carbon isbased on an ORP signal from an ORP sensor.
 36. The method of claim 33,further comprising an act of increasing the anoxic treatment timeperiod.
 37. The method of claim 36, further comprising an act ofdecreasing the anoxic treatment time period.
 38. A method of treatingwastewater, comprising: introducing the wastewater to an anoxicbiological treatment zone; introducing the wastewater exiting the anoxicbiological treatment zone to an aerobic biological treatment zone;passing at least a portion of the wastewater exiting the aerobicbiological treatment zone through a separator to produce a concentratedmixed liquor and a filtrate; and adjusting an effective volume of theanoxic biological treatment zone.
 39. The method of claim 38, whereinthe act of adjusting the effective volume of the anoxic biologicaltreatment zone comprises increasing the effective volume of the anoxicbiological treatment zone.
 40. The method of claim 38, wherein the actof adjusting the effective volume of the anoxic biological treatmentzone comprises controlling introduction of oxygen.
 41. The method ofclaim 38, further comprising introducing the wastewater to an anaerobicbiological treatment zone prior to introducing the wastewater to theanoxic biological treatment zone.
 42. The method of claim 38, furthercomprising recycling at least a portion of the concentrated mixed liquorto the aerobic biological treatment zone.
 43. The method of claim 39,further comprising the act of decreasing the effective volume of theanoxic biological treatment zone to a design condition.
 44. The methodof claim 40, wherein controlling introduction of oxygen is based on aflowrate of the wastewater.
 45. The method of claim 40, whereincontrolling introduction of oxygen is based on a predetermined timeinterval.
 46. The method of claim 40, wherein controlling introductionof oxygen is based on a concentration of a target constituent in thewastewater.
 47. The method of claim 42, further comprising recycling atleast a portion of the wastewater exiting the aerobic treatment zone tothe anoxic treatment zone.
 48. The method of claim 46, wherein thetarget constituent comprises ammonia.
 49. The method of claim 47,further comprising introducing biodegradable carbon to the wastewaterrecycled from the aerobic treatment zone to the anoxic treatment zonebased on a signal from a sensor.
 50. A wastewater treatment system,comprising: an anoxic treatment zone; an aerobic treatment zone fluidlyconnected to the anoxic treatment zone; a separator fluidly connected tothe aerobic treatment zone; and a controller in communication with anaeration system and configured to generate a first aeration controlsignal to allow increase of an effective volume of the anoxic treatmentzone during a first biological treatment mode of operation, and furtherconfigured to generate a second aeration control signal to allowreduction of the effective volume of the anoxic treatment zone to adesign condition during a second biological treatment mode of operation.51. The system of claim 50, further comprising a flowmeter disposed atan inlet of the anoxic treatment zone.
 52. The system of claim 50,further comprising a sensor disposed to monitor a concentration of atarget constituent in the wastewater.
 53. The system of claim 51,wherein the controller generates the first and second aeration controlsignals in response to a flowrate signal from the flowmeter.
 54. Thesystem of claim 52, wherein the controller generates the first andsecond aeration control signals in response to a concentration signalfrom the sensor.
 55. The system of claim 54, wherein the targetconstituent comprises ammonia.
 56. A method of facilitating treatingwastewater, comprising: providing a wastewater treatment system,comprising a first biological treatment zone, a second biologicaltreatment zone fluidly connected to the first biological treatment zone,a membrane module comprising a filter membrane fluidly connected to thesecond biological treatment zone, a recycle system fluidly connectingthe membrane module to the first biological treatment zone, and a sourceof biodegradable carbon fluidly connected to the recycle system.